\begin{tabular}{l*{5}{l}}
\toprule
                    &\multicolumn{5}{c}{}                                            \\
                    &$\tilde{z}_{n}^{(1)}$&$\tilde{z}_{n}^{(2)}$&$\text{Nunn}^{\text{con}}_{n}$&$\text{Nunn}^{\text{lib}}_{n}$&$\text{Levchenko}_{n}$\\
\midrule
$\tilde{z}_{n}^{(1)}$&        1.00&            &            &            &            \\
$\tilde{z}_{n}^{(2)}$&        0.93&        1.00&            &            &            \\
$\text{Nunn}^{\text{con}}_{n}$&        0.20&        0.03&        1.00&            &            \\
$\text{Nunn}^{\text{lib}}_{n}$&        0.22&        0.03&        0.99&        1.00&            \\
$\text{Levchenko}_{n}$&        0.13&        0.14&        0.68&        0.61&        1.00\\
\bottomrule
\end{tabular}
